Electronic warfare (EW) indicates the use of the electromagnetic spectrum in order deny its effective use by an adversary while optimizing its use by friendly forces. Electronic warfare has three main components: electronic support, electronic attack, and electronic protection. Electronic support (ES) is the passive use of the electromagnetic spectrum in order to gain intelligence regarding other parties on the battlefield in order to find, identify, locate and intercept potential threats or targets. Electronic attack (EA) is the active or passive use of the electromagnetic spectrum to deny its use by an adversary. Active EA includes such activities as jamming, deception, active cancellation, and EMP use. Passive EA includes such activities as the use of chaff, towed decoys, balloons, radar reflectors, winged decoys, and stealth. Electronic protection (EP) includes all activities related to making enemy EA activities less successful by means of protecting friendly personnel, facilities, equipment or objectives. EP can also be implemented to prevent friendly forces from being affected by their own EA. Active EP includes such activities as technical modifications to radio equipment (such as frequency-hopping spread spectrum). Passive EP includes such activities as the education of operators (enforcing strict discipline) and modified battlefield tactics or operations. ELINT Receivers One of the Electronic supports (ES) application is ELINT. It stands for ELectronic Signals INTelligence, and refers to intelligence-gathering by use of electronic sensors. ELINT focuses primarily on non-communications signals intelligence. Signal identification is performed by analyzing the collected parameters of a specific signal, and either matching it to known criteria, or recording it as a possible new emitter. The data gathered is typically pertinent to a rival's defence network, especially the electronic parts such as radars, surface-to-air missile systems, aircraft, etc. Gathering can be performed from ground stations near the opponent's territory, ships off coast, aircraft near or in their airspace, or by satellite. The ELINT receivers are used to search a broad range of frequencies for signals that may be emitted by a potential adversary. The frequency source in an ELINT receiver must be as noise-free as possible so as not to obscure weak incoming signals. The frequency source must also be extremely stable and accurate in order to allow accurate measurement of the incoming signal's characteristics. Emitters location The ability to locate radio and radar emitters is important in modern warfare. One method of locating emitters is to measure the time difference of arrival of the same signal at widely separated locations. Emitter location by means of this method depends on the availability of highly accurate clocks, and on highly accurate methods of synchronizing clocks that are widely separated. Triangulation is the process of finding coordinates and distance to a point by calculating the length of one side of a triangle, given measurements of angles and sides of the triangle formed by that point and two other known reference points, using the low of sinus. Since electromagnetic waves travel at the speed of light, 30 cm per nanosecond, the clocks of emitter locating systems must be kept synchronized to within nanoseconds in order to locate emitters with high accuracy. (Multi path and the geometrical arrangement of emitter locators usually results in a dilution of precision.) Without resynchronization, even the best available militarized atomic clocks can maintain such accuracies for periods of only a few hours. With the availability of GPS and using the "GPS common view" method of time transfer, widely separated clocks can be synchronized to better than 10 ns (assuming that GPS is not jammed). An even more accurate method of synchronization is "two-way time transfer via communication satellites," which, by means of very small aperture terminals (VSAT’s) and pseudo noise modems, can attain sub-nanosecond time transfer accuracies.

Print Version